FIG. 6 shows a structure of a conventional solid electrolytic capacitor. Next a manufacturing method of such solid electrolytic capacitor is described. Dielectric layer 13 is formed on porous valve metal 12 provided on a surface of valve metal foil 11. A conductive polymer layer is applied on dielectric layer 13 to form solid electrolyte layer 14, on which collector layer is formed consisting of carbon layer 15 and silver paste layer 16. The capacitor is then resin packaged to form outer package 17. External terminal 18 electrically connected to valve metal foil 11 is provided at the first end of outer package 17 and external terminal 19 electrically connected to collector layer is provided at the second end of outer package 17.
In such solid electrolytic capacitor, undesired solid electrolyte erroneously applied on protruding potion 11A of valve metal foil 11 during formation of solid electrolyte layer 14 causes electrical short-circuit or increases leakage current in capacitor. Insulating resinous protective layer 20 is generally provided on protruding potion 11A to prevent such a trouble.
Typically, coated and cured insulating resin such as epoxy resin or silicone resin, or insulating adhesive tape made of polyimide resin used as a base material serves as insulating protective layer 20. However, undesired solid electrolyte also is usually formed on the insulating resin or the insulating tape. This undesired solid electrolyte must be cleared by laser processing, but the processing may cause increase in leakage current. In addition, coated insulating resin partially permeates porous valve metal 12, which may impair capacitor characteristics due to, for example, uncontrollability of capacitance. In addition, the coating method lacks in workability and mass productivity.